Column-Parallel Image Sensor Initialization for Fixed Pattern Noise
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Solution Overview
Problem
In column parallel-type solid-state imaging devices, variation and noise can lead to vertical stripe-shaped fixed pattern noise (FPN) with column correlation, which is not adequately suppressed, affecting image quality.
Innovation Solution
A solid-state imaging device with unit pixels arranged in rows and columns, featuring vertical signal lines, first converters for digital signal conversion, an initialization voltage generator, and a noise addition mechanism that randomly changes bias current and initialization voltage for each row and column, introducing noise signals with varying levels to reduce quantization errors and initialization potentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the same processing circuit performs signal processing on image signals from unit pixels in the same column, then processing efficiency is improved, but vertical stripe-shaped fixed pattern noise with column correlation occurs
Solution Approach 1:
The patent applies local quality by making the initialization voltage different for each column while keeping it common for rows. Specifically, each column has a dedicated initialization voltage line connected to the initialization voltage generator, allowing independent control of initialization voltage per column. This local differentiation suppresses column-correlated fixed pattern noise while maintaining the column-parallel processing architecture's efficiency.
Solution Approach 2:
The patent changes the initialization voltage parameter for each column to suppress fixed pattern noise. The initialization voltage generator outputs different voltage levels to different columns, and this voltage parameter variation prevents the formation of vertical stripe patterns caused by uniform initialization across all pixels in a column.
2Adaptability or versatility
If analog pixel signals are converted to digital data by ADC converter, then signal processing capability is improved, but quantization errors and fixed pattern noise are introduced
Solution Approach 1:
The patent applies preliminary action by initializing the pixel signals before they are converted to digital data by the ADC converter. The initialization voltage is applied to the pixel signals through the vertical signal lines prior to conversion, which suppresses fixed pattern noise and reduces quantization errors before the digital conversion process occurs.
Data Source
AI summary
A solid-state imaging device configured to suppress fixed pattern noise having column correlation and/or lateral correlation from being generated in images is disclosed. In one example, a solid-state imaging device includes unit pixels arranged in row and column directions, vertical signal lines respectively connected to at least one of the unit pixels arranged in the column direction, first converters connected to the respective vertical signal lines and configured to convert an analog pixel signal into a digital pixel signal in reading each unit pixel arranged in the row direction, an initialization voltage generator that outputs an initialization voltage for initializing the unit pixels or input nodes of the first converters, and an initialization voltage line that connects the initialization voltage generator and the first converters. The initialization voltage generator changes the initialization voltage that is output for each row and/or column to be processed by the first converters.